This invention relates a device that is commonly referred to as a xe2x80x9clathxe2x80x9d, xe2x80x9cstickxe2x80x9d, xe2x80x9cstickerxe2x80x9d, or xe2x80x9ccrosserxe2x80x9d (referred to here as a xe2x80x9cseparatorxe2x80x9d) that is used in the lumber industry to separate pieces of lumber in a stack, bundle or lift or the like (hereafter referred to as a xe2x80x9cstackxe2x80x9d). More particularly, the invention relates to an improvement in such a lath to augment air circulation within a lumber stack and to reduce staining of lumber.
In the lumber industry timber is cut into boards or lumber which are usually stacked in a shed or kiln to dry before shipping. Stacking may also be used to maintain lumber during shipping or storage. The boards in a stack are usually separated by separators running transversely to the length of the boards. An individual stack is often built up to a height of about 5 feet with the boards laid in a spaced and parallel relationship in courses, course upon course, with separators laid between the courses across the boards. Individual stacks may be piled on one another to create larger stacks for efficient storage using spacer blocks between the individual stacks. The spacer blocks are usually larger than a common separator lath (4xe2x80x3xc3x974xe2x80x3 as opposed to 1xe2x80x3xc3x971xe2x80x3) but are usually made of the same material, ie. low grade lumber such as spruce. The difference in size of the separators is not material to this invention. Therefore, spacer blocks are also included within the meaning of the term separator, where the context permits, in this specification. Drying air circulates in the spaces between the boards in each course and in the spaces provided by the separators between the boards of adjacent courses and between individual stacks.
An imprint or stain, sometimes called a xe2x80x9cshadowxe2x80x9d or xe2x80x9csticker stainxe2x80x9d, may be left on a board in an area where it has been in contact with a separator in a stack. Such staining may be partly due to the percolation of sugars and other chemicals from the separators to the lumber. It is also understood that staining may result from the fact that air cannot penetrate to the board surface covered by a separator to dry the wood and mould or spores grow in the residual moisture. A stain may be visible immediately after removal of a board from the stack or it may show later during finishing or staining of the wood. It renders lumber unmerchantable for certain end uses and sometimes is the cause of costly claims to mills from customers. It is a significant problem in the lumber industry, particularly with light coloured woods.
Attempts to solve this problem have been directed at minimizing the contact area between a separator and the lumber in a stack. For example, U.S. Pat. No. 3,907,130 entitled xe2x80x9cKILN STICKERxe2x80x9d that issued to D. Hutcheson on Sep. 23, 1975, disclosed a plastic separator for drying wood with a curved upper surface and a lengthwise groove along its bottom surface to reduce the area of contact. One disadvantage of this design is that a lengthwise groove does not facilitate circulation of air through the groove. End to end circulation along the long length of a separator through a small cross section groove is inefficient. Consequently, the groove provides a protected area for mould and spores to cultivate. Another disadvantage is that equipment for manufacturing plastic separators is foreign to a lumber mill so a mill would need to buy prefabricated plastic separators from a remote factory. Manufacturing costs, transportation costs, availability, maintaining separator inventory at a mill and other factors augured against use of plastic separators and they did not replace the more common and readily available wooden separators.
Nevertheless, the lengthwise groove design to reduce contact area was adopted in the industry, but in wooden separators. It is not uncommon now to find wooden separators cut with top and bottom lengthwise grooves forming an xe2x80x9cHxe2x80x9d shaped cross section. The xe2x80x9cHxe2x80x9d separator reduces contact area and utilizes the wood resources of a mill but suffers the same disadvantage of poor air circulation along the long narrow grooves. The manufacture of such wooden separators may use equipment ordinary to a mill, but cutting lengthwise grooves requires close tolerances and straight separators to maintain the alignment of a groove to the long axis of a narrow separator. Further, manufacturing many separators may require many tools or many runs through the same tools.
It is an object of this invention to provide an improved separator for separating lumber that provides reduced contact area between the separator and the lumber, improved air circulation and permits simple manufacture without close tolerances using equipment commonly found at a mill. It is also an object of this invention to disclose elements to adapt a common plane or other apparatus to manufacture such improved separators. The disclosure of the invention is made in terms of wooden separators, because these are believed to be best suited to the lumber industry, but it will be appreciated by skilled persons that this disclosure is also suitable to and intended for separators manufactured from other suitable materials such as plastic except that the preferred manufacturing process may be unsuitable for some other materials.
The improved separator of this invention comprises a separator having a length to span across one or more pieces of lumber in a course and a height to separate the courses sufficiently for air circulation between the courses and having a plurality of grooves traversing the length of the separator to permit air circulation within the grooves. Since the grooves run across a short width of a separator rather than along its length, air circulation through the grooves is much improved over the prior art long groove separators. The grooves may run perpendicularly to the length of the separator or, diagonally, at an angle to the length. The spacing between grooves is not critical although close spacing reduces the contact area between grooves. In a preferred embodiment, the grooves are spaced to present sharp peaks between them thus minimizing the contact area with the lumber. In a preferred embodiment, grooves are cut with sharp peaks spaced about xc2xe of an inch and at a 60xc2x0 angle to the long axis of the separator. Similar grooves are cut in the top and the bottom surfaces of the separator to touch the boards in the lumber stack. In another embodiment, grooves are cut at a 60xc2x0 angle to the longitudinal axles of the separator in one direction and then cut again in an opposite direction to provide intersecting grooves. The ridges between the first run of grooves are cut by the traversing set of second grooves resulting in diamond shaped protrusions which further reduce the amount of surface area in contact with the lumber and provides for additional circulation. It will be appreciated that separator size, groove spacing and contact area should be sufficient to support the weight of the stack without denting the lumber to render it unmerchantable, but this aspect of design is within the skill of the art and will not be discussed in detail in this specification. It is similar to the design of a bed of nails that supports a heavy body with a delicate surface on sharp points on the principle that many points will support the weight of the body with little pressure on each point.
Manufacture of such separators is relatively easy. Since the grooves run transversely to the length of the separator there is no difficulty aligning the narrow separator to a tool during manufacture. Close tolerances are not necessary nor are multiple tools required. The separators may be cut in an ordinary plane fitted with a serrated blade that forms grooves and peaks as separators are passed sideways through the plane. The angle at which the separators pass through the plane determines the angle of the grooves to the long axis of the separator. The angle is not critical nor is consistency of the angle between separators, thus it is unnecessary to maintain close tolerances in the feeding process. The manufacture also has the advantage that it can be used to clean and renew old dirty separators for reuse as improved separators of this invention. Thus it is not necessary for a lumber mill to discard its inventory of separators to use this invention.